Phase III Trial of IGF-I for ALS The objective of this trial is to determine whether IGF-I slows progression of weakness in ALS. 300 patients with ALS will be enrolled for 2 years of treatment with study drug or placebo. The study will be double-blind, with equal randomization of patients to placebo or drug. The primary endpoint will be the rate of change in manual muscle testing score (MMT). Secondary endpoints will be tracheostomy free survival and change in ALSFRS score over the 2 year study period. Enrollment will be limited to those with a disease duration of less than 24 months and a manual muscle testing score of less than 8. The study is designed to detect a 30% difference in survival over the two year treatment period. Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder that causes progressive muscle weakness and death within 4 years of onset. Its overall incidence is about 2 cases/100,000 in the United States. Except for a very small minority of cases, the cause is unknown. The disease is incurable and only riluzole has proven to be effective in slowing the disease. Riluzole's effects are modest and more effective treatments for ALS are desirable. IGF-I had demonstrated neurotrophic effects in animal and tissue culture models of motor neuron disease. These findings have led to interest in its potential use in ALS patients. Clinical trials have been completed in the United States, Europe, and Japan with conflicting conclusions. Previous clinical trials in ALS have utilized global measures of function, electrophysiological measures of muscle function, mechanical measurement of maximum force generated by voluntary isometric contraction of muscle (MVIC) or manual muscle testing (MMT). Loss of function and death in ALS is primarily due to loss of muscle strength. Muscle strength is directly related to the underlying patholoj^ (loss of motor neurons). To obtain a definitive answer as to the beneficial effects of IGF-I in ALS, we will assess the most direct and objective effects of the disease directly by assessing muscle strength testing, survival and functional performance. The preliminary data from our prior trial allows design of a phase III treatment trial that will yield a definitive result about the treatment effect of IGF-I.